Single-piece injection molded rack

ABSTRACT

A single-piece, injection molded rack for holding test tubes or similar articles and a mold for producing the same. In a preferred three-tiered form, the intermediate tier is a lattice defined by the intersection of two superposed sets of parallel bars. These two sets of bars are formed by two pairs of correspondingly channeled slides that cooperatively engage to form a portion of the mold cavity corresponding to the lattice. The channels in each set of slides are aligned with the path of movement of the slides to permit their sliding, uniaxial movement relative to the molded bars. To further enable this sliding movement between mold segments and the molded rack, the connecting supports between the top tier and the intermediate tier are provided on the sides of the rack, while the connecting supports between the intermediate tier and the bottom tier are provided on the front and rear of the rack. With this arrangement, the slides that form the lattice of the intermediate tier are free to slide, as well, along the inner surfaces of the supports, which they also help to form.

BACKGROUND OF THE INVENTION

The present invention relates generally to the manufacture of injectionmolded articles and, more particularly, to a single-piece injectionmolded rack and the mold for producing the same. In a preferred form,the invention is advantageously employed to provide a plastic test tuberack for medical and laboratory use.

Test tube racks are widely used where it is desirable to performbiological or chemical tests in a related sequence or on a related groupof specimens. Before performing such tests it is frequently necessary tosimultaneously sterilize the test tubes and rack. Many operations, aswell, require that the rack, test tubes, and their contents be placed inan incubator to facilitate the chemical reaction or growth of organismswithin the media under test. Often, the autoclaves or incubatorsavailable to a particular laboratory have limited internal space, makingit highly desirable to have a rack that will hold a dense array of testtubes.

As test tubes are more tightly grouped, however, it becomes necessarythat the individual tubes be maintained in proper alignment so thatmaterial may be introduced or withdrawn from the tubes in an orderly,sequential manner. As well, the contents of the tube must remain readilyobservable by the technician.

The conventional wire rack is extensively employed in an effort toachieve these goals. Typically, such racks are three-tiered structures,the individual tiers being rectangular grids formed by welding togetherindividual metal rods. The tiers are then operatively joined by weldingadditional metal rods to each tier, vertically from top to bottom. Thecompleted assembly is thereafter coated with a thin layer of conformingplastic to protect the metal against corrosion and chemical attack.However, with usage, the plastic coating wears off, leading to rust andcorrosion which render the racks unusable.

While such wire racks function satisfactorily, they are costly toproduce and, because of their weight, costly to ship in quantity. Thesecosts are shared by the end user, making wire racks economicallyunsuitable for use as a disposable item of laboratory equipment. Theseracks, thus, are ill suited for analytical operations in which thehazardous substances used dictate disposal of both test tubes and racks.

For such hazardous procedures, test tubes made of plastic arecommercially attractive. Although a number of plastic test tube rackshas been heretofore proposed, none has achieved the dense packing andtube visibility advantages of the wire rack. The usual approach of suchplastic racks has been to provide multiple plastic plates, each of theplates having a plurality of apertures for receiving the test tubes.Typically, the apertures are circular to conform to the shape of thetest tubes. Often the plates are separately molded and thereafterassembled using other separately molded components. Since these singleplates are relatively thin, they are easily formed by a simple moldsection having projecting circular cores that cooperatively mate againsta planar mold half. The general design and construction of steelinjection molds, however, does not allow for compact and dense placementof metal cores to mold holes for various reasons. For example, the steelsections between the cores that mold the holes become too thin andflimsy for practical application. Also, the effective placement ofcooling channels becomes impractical. Consequently, these multilevelplastic test tube racks have generally widely spaced apertures and areassembled from several separately molded components.

In addition to the limitation on aperture density, this type of plastictest tube rack requires assembly, thus yielding up some of the costbenefits associated with plastic manufacture. It would be most desirableif a plastic test tube rack could be manufactured as a single piece in afully automated mold. It would be particularly advantageous if such arack could also provide the dense two-dimensional test tube arrays andhigh visibility afforded by wire racks.

The present invention achieves the objectives of equalling the test tubedensity and viewability advantages of the wire rack. In accomplishingthese objectives in a single-piece, one-shot injection moldingoperation, the present invention significantly reduces the manufacturingcost associated with assembling a wire rack from individual metal rodsas described above. As a consequence, the present invention provides arack that can be offered more economically to the end user. Since theunique configurations of both the rack and the mold are adapted to awide variety of plastic materials, racks can be produced to exhibitfunctional characteristics ranging from durability and reusability tosingle-use disposability.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a multitier rack forholding an array of test tubes or similar articles. Advantageously, therack is constructed as a single piece in a one-shot molding operation.The unique construction of the rack and, in particular, theconfiguration of the intermediate tier, permits close spacing of theapertures while at the same time minimizing the required thickness ofthe walls between apertures. An overall airy appearance results, greatlyfacilitating viewing the contents of test tubes held by the track. Whilethe invention will be described throughout with respect to athree-tiered rack, from the ensuing description it will become apparentto those skilled in the art that more than one intermediate tier may beincluded in the structure.

In accordance with an aspect of the invention, the intermediate tier isa lattice having apertures defined by the selective intersection of twosets of bars. As used herein, the term "set" is meant to encompass asingle bar, a group of bars, and an assemblage of groups of bars. In thepreferred embodiment, a top set of substantially parallel bars issuperposed over a bottom set of substantially parallel bars, at rightangles, to define generally rectangular apertures. When used inreference to bars, the phrase "substantially parallel" means that thelongitudinal axis of a bar is aligned parallel to the longitudinal axisof another bar (or to the longitudinal axes of other bars), or parallelto some other reference axis or plane. This preferred configurationenables formation of the intermediate tier with as few as two moldsegments. In simplest form, each set of bars is formed by a slide thathas parallel channels milled into a substantially planar surface. Thetwo channel-containing surfaces are moved into and out of face-to-faceengagement with each other along separate, single axial paths that areoriented relative to one another in accordance with the desired angle ofintersection of the two sets of bars. To yield the preferred latticewith rectangular apertures, the axial path of movement of the slideforming the bottom set of bars is perpendicular to the axial path ofmovement of the slide forming the top set of bars. Since all of thechannel-containing surfaces are substantially planar, when the mold isclosed, the respective surfaces mate perfectly in the regionscorresponding to the apertures in the lattice. Where the channels thatform the top set of bars overlap and intersect the channels forming thebottom set of bars, injected plastic flows freely to enable single-piececonstruction of the lattice. Since the channels are aligned parallel tothe axial path of movement of the slides, the bars that they form arelikewise oriented in parallel relation to the movement of the slide.Thus, when the molded rack has cooled, the slides are easily withdrawnaway from the molded rack and away from one another along theirrespective single axial paths with the channels sliding along the formedbars.

Since the lattice formed by these simply moved slides is withoutundercuts, it will be appreciated that a single-piece rack having morethan one intermediate tier may be easily formed. For such amultiple-intermediate tier arrangement, the bars on the facing surfacesof adjacent intermediate tiers would be parallel to one another and, inturn, parallel to the facing bars on the adjacent tier. For example, thetop bars on a given intermediate tier would be parallel to the bottombars on the intermediate tier immediately above it, while the bottombars thereof would be parallel to the top bars on the intermediate tierimmediately below it.

While the formation of the preferred configuration of superposedparallel bars has been described in relation to a single slide for eachof the top and bottom sets of bars, the invention contemplates the useof plural cooperating slides to form either one or both of the sets ofbars. In accordance with the preferred mold of the invention, each setof bars is formed by a pair of cooperating slides that are movable alongcoaxial paths in opposed directions relative to one another. Each bar isformed by a pair of channels (one channel being provided on each of theopposed slides), which mate end to end when the mold is closed. Insimilar fashion to the single slide arrangement, the pairs of channelsare aligned parallel to the axial path of movement of the opposedslides. Thus, when the molded rack is cooled, the slides are withdrawnin opposed directions away from one another and away from the moldedrack along their coaxial paths with the channels sliding over theportions of the bars they formed. This arrangement of cooperating pairsof slides advantageously permits the formation of supports between thetop and intermediate tiers and between the bottom and intermediatetiers. This is accomplished by providing channels in the mating faces ofthe cooperating slides. By selecting unequal lengths for the slideswithin a pair, the supports may be positioned where desired between thefacing surfaces of the tiers. As well, by selecting the number andconfiguration of channels in the mating faces of the slides, a pluralityof supports may be formed.

Although preferred, it is not essential that the bars within each of thesets be parallel. For example, where a set of bars consists of groups ofbars, the bars within a particular group may be parallel to one anotherbut not necessarily parallel to the bars within another group of theset. Similarly, it is preferred but not essential that the bars withineach set extend the full length between edges of the intermediate tier.

According to yet another aspect of the invention, to provide rigidity tothe rack and to maintain simplicity in the configuration of the moldsegments, the supports that join the tiers together do not extend thefull vertical span from top to intermediate to bottom tier. Instead, thetop tier is interconnected with the intermediate tier and, in turn, theintermediate tier is separately connected at another place to the bottomtier. In the preferred form, the top and intermediate tiers areconnected at their extreme side edges by side supports whose facinginner surfaces are substantially planar and parallel to one another.With this configuration, the side supports are readily formed by sidesurfaces of the mold slides that form the top set of parallel bars.Similarly, the supports connecting the intermediate tier to the bottomtier have substantially planar, parallel inner surfaces. As with theside supports between top and intermediate tiers, the supports betweenthe intermediate and bottom tiers are formed by front and back sidesurfaces of the slides that form the bottom set of bars. Thus, in thepreferred right-angle disposition of the two sets of bars forming theintermediate tier, the side supports and front and back supports havesurfaces lying in planes that are also perpendicular to one another.This arrangement not only simplifies mold design and enhances therigidity of the rack, but also aids the observation of the test tubecontents from different perspectives.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can best be understood by the following portion of thespecification taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a modified perspective view of one form of rack according tothe invention showing an exploded diagrammatic illustration of theinventive mold for the rack;

FIG. 2 is a modified perspective view of a preferred form of the rack;

FIG. 3 is a top plan view of the rack of FIG. 2;

FIG. 4 is a bottom plan view of the rack of FIG. 2;

FIG. 5 is a front elevational view of the rack of FIG. 2;

FIG. 6 is a left side elevation view of the rack of FIG. 2;

FIG. 7 is a partial cross-sectional side elevation view of the preferredmold in the closed position showing the molded rack;

FIG. 8 is a view similar to the view of FIG. 7, but showing the mold inthe open position;

FIG. 9 is a view similar to that of FIGS. 7 and 8, but showing the moldin the full ejection position, with the rack ejected;

FIG. 10 is a cross-sectional front elevation of a portion of the moldtaken along line 10--10 of FIG. 9 and illustrating in broken line theposition of the core slides when the mold is closed; and

FIG. 11 is a right side elevation view of an alternate slant rackembodiment of the invention, showing a held test tube and contents.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 diagrammatically illustrates the relationship and relativemovement among the mold segments that cooperate in the closed positionto form a mold cavity corresponding to the illustrated rack 10. Thiscooperative action can be appreciated more fully with a betterunderstanding of the configuration of the preferred rack illustrated inFIG. 1 and in greater detail in FIGS. 2 through 6.

To facilitate an understanding of this invention, the followingarbitrary directional convention has been adopted. The use of thisconvention is not, however, intended to limit the scope of the appendedclaims. With this in mind, in FIGS. 1 and 2, the elongate side of therack closest to the viewer is considered front, while the shorter sideof the rack closest to the viewer is considered left. Thus, from thesereference directions, the directions right, rear, upper, and lower onboth the rack and the mold follow the natural inclinations of the viewerfrom the given perspective.

As shown in FIG. 2, the rack includes a top tier 12, an intermediatetier 14, and a bottom tier 16, selectively interconnected inspaced-apart, superposed relation. For holding test tubes or similararticles, the top tier 12 and intermediate tier 14 have apertures 11 and13, respectively. These apertures are shaded, dimensioned, arrayed, andspaced according to the type, shape, and dimensions of the particulararticles to be held by the rack. For holding test tubes, as preferred,especially when the tubes are to be used for a battery of related tests,it is desirable to employ a dense two-dimensional array of apertures asshown in FIGS. 2 and 3. As a result of the unique configuration of theintermediate tier 14, the provision of rectangular or square aperturesis made possible, thus minimizing the thickness of the walls betweenadjacent apertures. When apertures 11 are square, as illustrated, thetop tier 12 is a rectangular grid having the appearance of two groups ofuniformly dimensioned and spaced parallel rods, which pass through eachother at right angles.

As will be discussed more fully hereinafter, it is preferred that thesegments of the mold that form the intermediate tier 14 also cooperatewith additional mold segments to form the top tier 12. Generally, thesemold segments are slides that, during the molding operation, occupy whatwill become the space between the top and intermediate tiers. When themolded rack has cooled, these slides must be withdrawn from this space(or the molded rack pulled from the slide). According to one form of themold, a single slide is employed to form a top set of bars 15 of theintermediate tier 14. The upper surface of this slide is substantiallyplanar and has a slight draft angle to facilitate its removal. When sucha single slide is employed, it will be seen that the lower surface 50 ofthe upper tier will be substantially planar. It is preferred, however,that a pair of cooperating slides be utilized to form the top set ofbars 15 of the intermediate tier and the lower surface 50 of the uppertier. Referring to FIG. 6, when the mold is closed, these two slidesmeet at a centrally located parting line 56. For ease of removal, aslight draft angle is provided on the upper surfaces of these twoslides. When such slides are employed, the lower surface 50 of the toptier has two distinct planar surfaces that taper inwardly and downwardlytoward the intermediate tier 14 from the front edge 52 and back edge 54,meeting, or intersecting, at the parting line 56. Although it ispreferred that these front and rear portions of the upper surface 50 ofthe top tier slope downwardly and inwardly at an angle of about one-halfto two degrees, if desired, the angle can be significantly larger. Aswill be discussed more fully hereinafter, although preferred, it is notessential that the parting line 56 be centrally located. However,whenever two or more slides are employed to form the lower surface 50 ofthe top tier, it is preferred that the formed front and rear portions ofthe surface 50 include angles that will facilitate withdrawal of theslides.

Referring once again to FIG. 2, the intermediate tier 14 is a latticedefined by intersecting sets of top bars 15 and bottom bars 17. The bars15 and 17 are aligned, within their respective sets, along parallel axesthat lie generally within the same horizontal plane. The two sets ofbars intersect, preferably at right angles, to define rectangular,preferably square, apertures that precisely map the array of apertures11 in the top tier, as illustrated by their hidden appearance whenviewed from the top as shown in FIG. 3. It is preferred that the barshave a generally uniform, rectangular cross-sectional shape in order toprovide generally planar surfaces which will permit easy, slidingwithdrawal of the mold segments. It is to be understood, however, thatthe bars may be configured with other cross-sectional shapes such as,for example, substantially circular or semicircular, square, triangular,trapezoidal and the like. As with the apertures 11 in the top tier, theapertures 13 of the intermediate tier can be arranged, spaced, sized,and shaped differently to accommodate different test tubes or articles.For example, it may at times be desirable to form intermediate tier 14in a fashion such that either alternate top bars 15 or bottom bars 17are omitted in order to permit the storing of test tubes at an angle.The preferred symmetrical correspondence of the array of apertures 11and the array of apertures 13 is generally preferred for test tubes inorder to provide an orderly arranged, and visually uncluttered,assemblage of test tubes. To facilitate record keeping, the uppersurfaces of the front, back, left side, and right side edges, whichdefine the periphery of the top tier 12, may include alphanumericinscriptions or labelling (not shown) adjacent the outer apertures toprovide row-column matrix identification of the test tubes.

In keeping with an objective of simplifying the design of the moldparts, it is preferred that the upper surfaces of the bottom bars 17 andthe lower surfaces of the top bars 15 lie generally within the samehorizontal plane. As will be explained more fully hereinafter, but whichcan be briefly understood by viewing FIG. 1, the planarity of thesesurfaces permits sliding, uniaxial movement of the mold components thatform the top bars 15 and bottom bars 17 of the intermediate tier. Whenmore than a single mold component is used to form the bars, it may bedesirable to have the upper surfaces of the bottom bars 17 and the lowersurfaces of the top bars 15 lie other than within the same plane.

Referring again to FIG. 2, the bottom tier 16 also includes an array ofapertures 18 that are aligned operatively, in selective fashion, withthe apertures 11 and 13 in the top and intermediate tier, respectively.By "operatively aligned" or "aligned operatively", it is meant thatselected apertures in a given tier are positioned in relation toselected apertures in another tier (or in other tiers) to hold testtubes or other articles in one or more predetermined positions. Theapertures 18 are here shaped with rounded ends to provide receptaclesfor the rounded ends of test tubes. Inclusion of apertures orreceptacles in the bottom tier is not essential, but is preferred toprovide a more positive hold on the test tubes.

In similar fashion to the lower surface 50 of the top tier 12, thebottom tier 16 has an upper surface 19 that may take one of severalforms. For example, this surface may be substantially planar, slopingslightly toward one or the other of its ends or may have substantiallyplanar left and right side portions that angle inwardly from the leftand right side edges, respectively, and upwards toward the intermediatetier, intersecting at a parting line. This parting line may be locatedcentrally or positioned toward the left or right side edge of the bottomtier.

The top tier is connected to the intermediate tier by side supports 20.In the FIGS. 2 through 4 embodiment, two side supports 20 are includedon the left and right sides of the rack (left being the closest, exposedside in FIG. 2). A single side support (as shown in FIG. 1) or two ormore side supports may be utilized. The two-support arrangement of FIG.2 provides sufficient rigidity to the ends of the rack while permittingobservation of the tubes from the ends. Optionally, the space betweensupports 20 may partially be filled with a tab (either depending fromthe top tier or extending from the intermediate tier). Such a tab wouldbe used to bear legends indicating, for example, hazardous contents inthe test tubes or the manufacturer's identification.

Although preferred, it is not essential that the top and intermediatetiers be connected at their left and right side edges. Thus, forexample, interconnection of these tiers could be accomplished by one ormore supports positioned inwardly from either or both of the left andright side edges of the tiers. Thus, in simplest form, the top andintermediate tiers may be interconnected by a single support that can belocated at aligned edges of the two tiers, inwardly of the edges of bothtiers, or extending from the edge of one tier to a position inward ofthe edges of the other tier. As will be discussed more fullyhereinafter, it is not essential that the three tiers have substantiallythe same peripheral shape and dimensions or that the edges of the tiersbe aligned substantially coplanar. In such instances, the side supports20 (whether located at the edges or inward therefrom) may have aconfiguration and alignment other than as shown in FIG. 2. For example,if the left side edge of the intermediate tier were extended outwardrelative to the left side edge of the top tier, the side supports 20could either slope smoothly downward and outward or follow a sharpS-curve downward and outward from the top to the intermediate tier.

It will, thus, be seen that a wide variety of means may be provided forinterconnecting the top and intermediate tiers. Again, in keeping withthe goal of simplifying the design of the mold, it is preferred that theside supports 20 be arranged so that they may easily be formed by theside surfaces of the slide (or slides) that form the top bars 15 of theintermediate tier. Since these slides are withdrawn along an axis thatis aligned parallel to the axes of the top bars 15, it is preferred thatthe side supports 20 have their inner surfaces aligned parallel with theaxes of the top bars 15 so that the slides may also be easily withdrawnalong these inner surfaces. In similar fashion to the formation of thelower surface 50 of the top tier and the upper surface 19 of the bottomtier, the inner surfaces of the side supports may have eithersubstantially planar inner surfaces or substantially planar front andrear surface portions that intersect at a parting line. Where the sidesupports 20 are located inwardly of the edges, it may be desirable thatboth the inner and outer surfaces thereof be aligned with the axial pathof movement of the slides that form them. In all such arrangements thatutilize the slides forming the bars 15 to also form the side supports20, it is essential only that the supports be formed without undercuts.

The intermediate tier is connected to the bottom tier by two frontsupports 21 and two rear supports 22, only one of which is shown in FIG.2. Although not essential, the front and rear supports (and the sidesupports 20) may include vertical ribs for added strength and radiused,or beveled, corners for internal strain relief. In the preferredconfiguration of FIG. 2, the front supports 21 and rear supports 22connect the front and rear edges, respectively, of the intermediate andbottom tiers. The outer edges of both pairs of supports are alignedsubstantially coplanar with the edges of the tiers that they connect. Itwill be appreciated from the preceding discussion of the side supports20 that the front supports 21 and rear supports 22 may have a wide rangeof configurations. Thus, there may be one or more supports at the frontor rear edges, one or more supports located inward of the front and rearedges of the bottom and intermediate tiers, or a combination of supportsat the edges and inward of the edges. Since it is preferred that theslide or slides that form the bottom bars 17 also help to form the frontand rear supports 21 and 22, it is also preferred that the innersurfaces of the supports 21 and 22 be aligned with the axial path ofmovement of the slides. As shown in FIG. 6, in the preferred rack, theinner surfaces of the supports 21 and 22 have substantially planar innersurfaces that are aligned substantially parallel to the axes of thebottom bars 17.

Referring to FIG. 11, there is shown one example of a modified rack inwhich the front support 101 has an inner surface that is not alignedparallel to the bottom bars 102, but is aligned with the axis of theslide, (which slide is operatively withdrawn outward toward the viewer).In this modified form, the rack is used as a slant rack for holding testtubes and their contents at a predetermined angle (one such tube 100 andits contents are shown). As illustrated, the modified intermediate tier106 extends outward relative to the top tier 107 and bottom tier 108(both of which are substantially unmodified). Either the entire frontedge of the intermediate tier 106 or a portion thereof (for example, apost) may form the outward extension. In either of these arrangements,it is preferred that the support 101 extend from the front edge of thebottom tier 108 at an angle outward to the extension 102 of theintermediate tier 106. In this preferred construction, the front surfaceof the support 101 provides a stable surface for supporting the rackwhen tilted onto a table or other surface 104, as shown in FIG. 11. Theinvention is particularly well suited to providing a range of slantangles, the approximately 20-degree angle illustrated in FIG. 11 beingone such example. A close examination of FIG. 11 reveals that theintermediate tier 106 also has a rear extension 105 that projectsoutward from the bottom and top tiers. The rear support 103, whichconnects the extension 105 to the rear edge of the bottom tier 108, isinclined at an angle of about five degrees. Thus, when the rack istilted onto the outer surface of the rear support 103, the test tubesand their contents are oriented at about five degrees. Again, it ispreferred, but not necessary, that the support 103 extend between theoutside edges of the extension 105 and bottom tier 16. For example,either support 103 or support 101 could alternately extend at rightangles relative to the intermediate and bottom tiers.

As suggested by the modified rack of FIG. 11, the invention is wellsuited to provide multitier racks having a variety of configurations.The arrangement of the top and bottom sets of bars advantageouslypermits the placement of interconnecting supports at various locationsalong and within the edges of the tiers. Although the invention has beendescribed in relation to a three-tiered structure, which structure hassubstantially parallel tiers having the same general rectangularperiphery and having edges that are aligned substantially coplanar, theinvention encompasses a broad range of shapes, dimensions, and alignmentof the tiers. Although the arrangement of the preferred rack of FIGS. 1through 6 is particularly helpful in simplifying the design of the moldthat forms it, it may be desirable to absorb the added cost of a morecomplex mold in order to configure the rack other than as illustrated.For example, it may be desirable to extend one or more of the edges (oronly a portion thereof) of one or more of the tiers. In such instance,the edges of the tier, or tiers, so extended would have other than acoplanar alignment with the edges of the other tiers. By way of anadditional example, it is also not necessary that the tiers be generallyparallel, or horizontal. Thus, any of the tiers, including theintermediate, may be arranged at an angle relative to either of theother tiers.

Although the invention has been described in relation to the preferredrack and in terms of the arbitrary directional convention adoptedtherefor, it is to be understood that the inventive concepts and theappended claims broadly cover a rack having a plurality of spaced-apart,selectively interconnected tiers, at least one intermediate tier ofwhich has a top set of bars and a bottom set of bars. Importantly, it isnot essential that the bars within each set be parallel to one anotheror that such bars extend the full distance between edges of theintermediate tier. Thus, for example, either or both of the top andbottom sets of bars may consist of groups of bars, the bars within eachgroup being substantially parallel to one another. Although theconfiguration of the intermediate tier with such groups of parallel barswould complicate mold design, it would provide a greater variety ofconfigurations for the apertures within a given rack and, hence, providea means for holding or grouping of test tubes or other articles havingdivergent shapes. Since the individual bars within a given group wihinthe top set of bars would not necessarily overlap each of the barswithin the bottom set (or groups of bars within the bottom set), therewould be only selective intersection and superposition of the variousbars. That is to say, only selected bars within the top set would besuperposed over and intersect with selected bars within the bottom setto define the apertures.

An important aspect of any such arrangement is that the bars making upthe lattice of the intermediate tier contain no undercuts. In thecontext of this disclosure, undercuts mean protrusions that will preventthe withdrawal of the mold segments that form the components of therack. Although the invention is intended to encompass any single-pieceinjection molded rack, the intermediate tier of which has selectivelysuperposed and intersecting top and bottom sets of bars, it is preferredthat there be no undercuts in the lattice of the intermediate tier inorder to enable the formation thereof with slides, which moveuniaxially.

As shown most clearly in FIGS. 5 and 6, further strengthening of therack is obtained by including an upper spacer or column 24 extendingbetween the top and intermediate tier and a lower spacer 26 extendingbetween the intermediate tier and the bottom tier. While the spacers 24and 26 may have a variety of cross-sectional shapes, such as circular,square, triangular, or even a long thin rectangular plate, which wouldgive the appearance of a wall, the illustrated spacers resemble a crossin cross section and, accordingly, exhibit good rigidifying strength.For added structural strength, the top tier optionally includes a gusset28 that depends from the lower surface 50 and extends frontward andrearward from the spacer 24, spanning a portion of the front to reardimension of the surface 50. While only one centrally located gusset 28is shown in FIG. 5, it may be desirable to include more than one suchgusset at spaced intervals along the lower surface of the top tier. Asillustrated in FIG. 2, a gusset 29 may also be optionally provided,upstanding from one or more of the top bars 15. When so provided, thegusset 29 as well as the central gusset 28 may be formed as outwardextensions of the upper spacer 24.

As shown in FIG. 4, posts 23 and elongated feet 25 may optionally beincluded on the lower surface of the bottom tier 16. In addition toelevating the rack, the posts and spacers may be advantageously shapedand positioned to provide an interlocking fit with the apertures 11 inthe top tier of another rack for stacking purposes.

The rack in accordance with the invention can be made from any suitableinjection molding material, such as, for example, polyethylene,polypropylene, polystyrene, high-impact polystyrene, polycarbonate,polyamides, polyacetals, polyurethane, and the like. The injectionmolding material can also contain fillers, glass fibers, carbon black,carbon fibers, boron fibers, silica, titanium dioxide, and the like.Glass fibers are a preferred filling material.

FIGS. 7, 8, and 9 illustrate, in partial cross-sectional side elevation,the mold components and the sequential operation thereof to produce theinventive rack. As noted earlier, FIG. 1 diagrammatically illustratesthe movement and relationship of these components and will be referredto to facilitate an understanding of the more detailed views of FIGS. 7through 9. As an aid in understanding this mold, certain features of themold have been simplified or not shown. As well, for purposes ofclarity, some sectional portions of the mold (and the molded rack inFIGS. 7 and 8) have not been cross-hatched. Also, since the gatingmethods and techniques for introducing the molten plastic material intothe mold are conventional, they are not shown or described in detailherein. Preferably, a three-plate runner mold system is employed,although other systems may be used. As well, the mold may be readilyadapted for use in a wide variety of injection molding machines thatoperate in either a vertical or horizontal manner and with any suitableinjection moldable material. The FIGS. 7 through 9 illustrate thepreferred disposition of the mold in a horizontal-type injection moldingmachine.

Referring initially to FIG. 8, the mold includes a stationary, orinjection, half generally designated 40 and a movable, or ejection, half42. The ejection half 42 is movable along an axial path determined byfour parallel leader pins 44 that are slidably journalled in boreslocated adjacent the corners of the mold. Movement of the ejection halfalong the leader pins between the mold open position of FIG. 8 and themold closed position of FIG. 7 is controlled by means of a conventionalhydraulic apparatus that is not shown. The distance travelled by theejection half 42 is somewhat foreshortened in the FIGURES, but ispreferred to be about two to two-and-one-half times the dimension of themolded rack to facilitate ejection thereof.

Injection half 40 includes a runner system 41 through which plasticmaterial is introduced into each of the portions of the mold cavity thatform the three tiers. A rear slide 43 projects outwardly from a cavity45 of the injection half. The lower surface 46 of the rear slide issubstantially planar and aligned generally parallel to the axial path ofmovement of the ejection half 42. As shown in FIG. 1, channels 47 aremilled into the lower surface 46 of the rear slide. These channels 47correspond in cross-sectional dimension to the cross-sectional dimensionof the top bars 15 of the rack and in length to a predetermined portionof the overall length of the top bars. The channels 47, i.e., thelongitudinal axes thereof, are aligned parallel to the axial path ofmovement of the ejection mold half 42. This alignment is illustrated inFIG. 1 where the path of movement of the ejection half is in thedirection of the arrow extending from rear slide 43 into the spacebetween the top and intermediate tiers of the rack 10. It is to beunderstood that this arrow, as well as the other arrows in FIG. 1,illustrate the relative (not necessarily actual) movement between therack and the parts of the mold which form it. For example, during themold-opening operation, the rear slide 43 (as part of the injection moldhalf) remains stationary while the ejection half (and the still captivemolded rack) are moved in the direction of the arrow just discussed. Theremaining components in FIG. 1, which will be identified and describedin detail hereinafter, are part of the ejection half 42 of the mold.Briefly, these elements are front slide 31, left core slide 60, rightcore slide 70, upper slide block 80, and lower slide block 90.

As seen best in FIG. 9, front slide 31 is formed as part of retainerblock 30 and is flanked by an upper cavity 32 and a lower cavity 33. Inthe mold closed position, the front slide 31 cooperatively engages rearslide 43 in face-to-face relation to define the portion of the moldcavity that forms the top bars 15 of the intermediate tier. To form thisportion of the cavity, the lower surface 34 of the front slide 31 (seeFIG. 10) includes parallel channels 35 that, in identical fashion to thechannels 47 of the rear slide 43, correspond in cross-sectionaldimensions to the cross-sectional dimensions of the top bars 15. Whenthe front and rear slides are engaged in the mold closed position, thechannels 35 in the front slide mate end to end with the channels 47 ofthe rear slide to form channels that correspond in length to the desiredlength of the top bars. While the bar length-determining function may beapportioned between the front and rear slides, as discussed below, it ispreferred that each of these slides forms half of the top set of bars.Similarly, the longitudinal axes of the channels 35 are parallel to oneanother and to the axial path of movement of the ejection half 42 of themold. The axes of the channels 35 lie within a plane that issubstantially parallel to the plane of lower surface 34. As suggested inFIG. 1, it is preferred that the front slide 31 and rear slide 43 bemirror images of one another and engage along a parting line that runscentrally through the cavity that forms the rack (which corresponds withthe parting line 56 on the rack, as shown in FIGS. 5 and 6). Thisparting line is coincident with the parting line between the retainerblock 30 and the injection half 40, and is indicated by the linelabelled PL in FIGS. 8 and 9. It is to be understood that the front andrear slides may be arranged to engage along a parting line that is notcentrally located and that is oriented in a plane that lies other thangenerally perpendicular to the direction of movement of the ejectionhalf. For example, the mating faces of the front and rear slides may beoriented in planes that are parallel to one another but at an anglerelative to the path of movement of the ejection half. In such instance,adjacent channels on each slide would gradually increase in length froma shortest channel to a longest channel. When the two slides areengaged, the shortest channel of one slide would mate with the longestchannel of the other slide in progressive fashion. Alternately, theengaging faces of these slides could be inclined toward one another sothat the upper surfaces engaging at a parting line that is offset(either to the front or to the rear) from the parting line of the lowersurfaces.

As mentioned above, in preferred form, the front and rear slides eachform half of the cavity corresponding to the top set of bars 15.Advantageously, the central engagement of the front and rear slidespermits the inclusion of vertical channels 48 and 36 that cooperativelyform the portion of the mold cavity corresponding to the upper spacer 24of the rack.

The upper surface 49 of the rear slide and the upper surface 37 of thefront slide are each substantially planar and cooperate with the upperslide block 80 to form the portion of the mold cavity corresponding tothe top tier 12 of the rack. To facilitate separation of the molded rackfrom the front and rear slides, the surfaces 49 and 37 preferablyinclude a draft angle that tapers inwardly and downwardly toward theparting line, i.e., toward the respective engaging faces of the rear andfront slides. The draft angles are preferably slight, from about 0.5 totwo degrees in order to provide a generally planar appearance to thelower surface 50 of the top tier. In actuality, however, the presence ofthese draft angles molds distinct planar front and rear portions of thelower surface of the top tier. If desired, of course, a much largerdraft angle could be utilized.

To form the gusset 28 on the underside of the top tier, the uppersurface 37 of the front slide and the upper surface 49 of the rear slidecontain milled grooves, as shown in FIG. 1, which dimensionallycorrespond to the desired dimensions of the gusset. If more than onegusset is desired, additional channels may be provided on these twosurfaces. In similar fashion to the channels that form the top bars 15,the channels that form such gussets are aligned parallel to the axialpath of movement of the ejection mold half so that the front and rearslides may be slidingly separated from the molded gussets.

It will be appreciated that, rather than the single vertical channels 36and 48, the front slide 31 and rear slide 43 could optionally include ontheir engaging faces plural channels to form multiple upper spacers or,if desired, a single solid support that spans the entire length of thetop and intermediate tiers. Various forms of providing such alternatespacers and including rigidifying and stress-relieving features thereforwill be appreciated to those skilled in the art. It will be furtherappreciated that, rather than the symmetrical arrangement of the frontslide 31 and rear slide 43, a single slide could be used to form the topbars 15. Such a slide would include channels that span the entirefront-to-rear length of the upper bars 15. Employment of such a slide,would, however, not permit the formation of centrally located spacersbetween the top and intermediate tiers.

The left core slide 60 and right core slide 70 cooperate in similarfashion to the front and rear slides to help form the bottom bars 17 ofthe intermediate tier. As seen most clearly in FIG. 1, the uppersurfaces 61 and 71 of the left and right core slides, respectively,include parallel channels 62 and 72, respectively, which mate end-to-endto define the portion of the mold cavity corresponding to the bottombars. These channels correspond in cross-sectional dimension to thecross-sectional dimension of the bottom bars and in length topredetermined portions of the overall length of the bars. To permitseparation of these slides from the molded rack, the channels arearranged with their longitudinal axes parallel to the axial paths ofmovement of the core slides 60 and 70. Preferably, the core slides aremovable along coaxial paths in opposed directions relative to oneanother and at right angles to the axial path of movement of theejection half. If it is desired to form a rack having top and bottomsets of bars which intersect at other than right angles, then the axialpaths of movement of the core slides would be oriented at some otherangle relative to the axial path of movement of the ejection half. Asshown in FIG. 10, the core slides 60 and 70 move from their respectiveclosed positions 60' and 70' shown in connected broken line, to theiropen positions shown in solid line, in which these slides are fully awayfrom the molded rack (not shown in FIG. 10). In viewing FIG. 10, inrelation to FIGS. 7, 8, and 9, it is helpful to note that, because ofthe direction of view and the arbitraily adopted directional convention,the right core slide 70 appears on the viewer's left in FIG. 10, whilethe left core slide 60 appears on the viewer's right. Also, in the moldclosed position of FIG. 7, the section is taken through the left coreslide 60, while, in FIGS. 8 and 9, the left core slide 60 has beenremoved from view by virtue of the section (line 9--9 in FIG. 10). Sincethe right core slide 70 has been withdrawn in FIGS. 8 and 9, the vieweris looking at the face of this slide in these figures (a portion of thisface being hidden by the yet to be ejected rack in FIG. 8).

Again, in analogous fashion to the provision of substantially planarupper surfaces on the front and rear slides, the lower surfaces of theleft and right core slides are each substantially planar but notnecessarily coplanar with one another. To permit separation of the coreslides from the molded rack, a slight draft angle is also preferablyprovided for the lower surfaces 63 and 73. Thus, the surfaces 63 and 73each taper inwardly and upwardly toward the parting line of the left andright core slides.

From FIG. 1 it will be seen that these lower surfaces 63 and 73cooperate with the lower slide block 90 to form the bottom tier 16, theapertures therein being formed by the projecting pin cores 91. The uppersurface 19 of the bottom tier formed by the lower surfaces 63 and 73 hasdistinct, substantially planar, left and right portions which intersectat the centrally located parting line. When the preferred draft angle offrom about 0.5 to 2 degrees is used, the slight deviation of the moldedsurface 19 from a true plane is discernible only upon close visualinspection. Of course, if desired larger draft angles may be used.Rather than the pair of cooperating core slides 63 and 73, a singleslide may be employed to form the bottom bars of the intermediate tierand the upper surface of the bottom tier. The lower surface of such asingle slide would also include a draft angle to permit facileseparation from the upper surface of the bottom tier.

To form the preferred, centrally located lower spacer 26 of the rack,the engaging faces of the left and right core slides include verticalchannels 64 and 74, respectively, which mate in the mold closedposition. Rather than the single vertical channels 64 and 74, the leftand right core slides could optionally include on their engaging facesplural channels to form multiple lower spacers or, if desired, a singlesolid, wall-like support that spans the entire front-to-back width ofthe intermediate and bottom tiers. It will be appreciated by thoseskilled in the art that the number, configuration, and positioning ofthese spacer-forming channels may be varied greatly. In the preferredrack, the bottom tier has sufficient rigidity so that additional gussetsare not needed. It will be understood, however, that it may be desirablewith a less rigid configuration of the bottom tier to include gussets onthe upper surface 19 of the bottom tier. In similar fashion to theformation of the gusset 48, such gussets for the bottom tier may beformed by suitably milling channels into the lower surfaces 63 and 73 ofthe core slides, either as extension of the channels 64 and 74 or asseparate channels. As with the front and rear slides, the left and rightcore slides may have unequal lengths so that their respective channelsform unequal lengthwise portions of the bottom bars. As well, theengaging faces of the core slides may meet in a plane that is inclinedat an angle relative to the coaxial paths of movement of these twoslides. Additionally, the engaging faces of these two slides may beinclined toward one another so that the upper surfaces 61 and 71 engageat a parting line that is offset (either to the left or to the right)from the parting line of the lower surfaces 63 and 73. A similararrangement may, of course, be employed for the front and rear slides 31and 43. To form the side supports 20 between the top and intermediatetiers, the left and right core slides include vertical surface portions65 and 75, respectively, which have milled side channels 66 and 76,respectively, as shown best in FIG. 1. When the mold is closed, theright side channel 76 cooperates with the right side surface portions ofthe front and rear slides, 31 and 43, respectively, to form the portionof the mold cavity corresponding to the right side support. Similarly,the left side channel 66 cooperates when the mold is closed with theleft side surface portions of the front and rear slides to form theportion of the mold cavity corresponding to the left side support of therack. It will be recalled that the FIG. 1 embodiment of the rackillustrates a single side support for purposes of clarity in thisFIGURE. For the preferred mold, which yields the rack of FIG. 2, thesurfaces 65 and 75 would have a pair of channels corresponding to thetwo side supports 20 on each of the left and right sides of the rack. Itcan be seen that a wide variety of configurations for the side supportmay be realized by altering the vertical surfaces 75 and 65 of the twocore slides. As well, the location of such side supports may bepositioned inwardly from the side edges by altering the surfaces 65 and75 of the core slides and the respective side surfaces of the front andrear slides with which they engage. For example, by providing aprojection from the surface 75, and by suitably altering the right sidesurfaces of the front and rear slides, the right side support may bemoved inward from the right side edges of the top and intermediate tier.By arranging the surfaces 65 and 75 at an angle other than the generallyvertical angle suggested in FIG. 1, the side edges of the intermediatetier may be moved outward relative to the side edges of the top tier.Such a reconfiguration would, of course, also incline the side supportsat an angle. One skilled in the art will appreciate that many suchmodifications may be made, subject only to the general requisite thatundercuts on the inner surfaces of the left and right side supports beavoided in order to permit withdrawal of the front and rear slides 31and 43.

The front and rear supports 21 and 22, respectively, are formed in ananalogous fashion by channels which are formed in vertical surfaceportions 39 and 69, respectively, of the rear and front slides, 43 and31, respectively. Only one channel 38 on the rear slide is clearly seenin FIG. 1, it being appreciated that there is a pair of channels in thissurface, as well as a pair of channels in the surface portion 69 of thefront support. In identical fashion to the surfaces of the left andright core slides that form the side supports, the vertical surfaceportions of the front and rear slides that contain the channels may bevariously configured to provide a wide variety of front and rearsupports. For the illustrated preferred arrangement, and for all suchmodifications, the vertical surface portion 39 of the rear slide, whichcontains the channel 38, cooperates when the mold is closed with rearsurface portions of the left and right core slides 60 and 70, while thevertical surface portion 69 of the front slide 31, which contains thechannels (which are not seen) cooperates when the mold is closed withfront surface portions of the left and right core slides. It will beseen that one such modification would provide a mold for forming themodified rack of FIG. 11. Although not illustrated in FIG. 1, it will beunderstood that the channels which form the front and rear supports arepreferably configured to yield the front and rear supports illustratedin FIG. 2.

Referring to FIGS. 7 and 8, the upper slide block 80 and lower slideblock 90 are releasably held within the upper cavity 32 and lower cavity33, respectively, of the retainer block 30. These slide blocks remainseated in the retainer block while the ejector half moves from the moldclosed position of FIG. 7 to the mold open position of FIG. 8. To permitseparation of the upper and lower slide blocks from the molded rack 10(see FIG. 8), the upper slide block 80 and lower slide block 90 aremovable relative to the retainer block 30 along paths determined byupper angular ejector pin 81 and lower angular ejector pin 92,respectively. Both upper and lower angular ejector pins are slidablyjournalled in respective bores that are disposed at an angle withrespect to the axial path of movement of the ejection mold half.Journalling of the angular ejector pins is accomplished with upper boss82 and lower boss 93. The angular ejector pins 81 and 92 are secured attheir forward ends within upper slide block 80 and lower slide block 90,respectively. At their rearmost ends, the angular ejector pins areconventionally secured in T bushings to permit vertical travel of theends when the ejector pins are driven forward through the angular pathin the retainer block 30. The sequence of movement of the angularejector pins 81 and 92 is shown in FIGS. 8 and 9. From the mold openposition of FIG. 8, the angular ejector pins 81 and 92 are drivenforward by the forward travel of the ejector box 85, which travels alonga path determined by leader pins 86 (preferably four, as shown in FIG.10). This technique for ejecting angular pins and the construction ofejector box 85 are conventional and, accordingly, will not be describedin detail herein.

Upon completion of the travel of the angular ejector pins 81 and 92, theupper slide block 80 and lower slide block 90 are displaced away fromone another and away from the molded rack. In reaching this fully open,or ejection, position, the two slide blocks 80 and 90 follow the angularpath defined by the bores through retainer block 30. This actionwithdraws the projecting pin cores 91 from the apertures formed in thebottom tier of the rack and also pulls the projecting pin cores 83 fromthe apertures formed on the top tier of the rack. As will be seen mostclearly in FIG. 1, the projecting pin cores 83 on the upper slide blockcooperate with the upper surfaces 37 and 49 of the front and rearslides, 31 and 43, respectively, to define the portion of the moldcavity corresponding to the upper tier. Similarly, the projecting pincores 91 on the lower slide block 90 cooperate with the lower surfaces63 and 73 of the left core slides, 60 and 70, respectively, to definethat portion of the mold cavity corresponding to the bottom tier of therack.

To strip the molded rack from its engagement with the front slide 31,plural ejector blades 95 are slidably journalled in retainer block 30 inconventional fashion, the ejector blades 95 are activated by the ejectorbox 85 simultaneously with the angular ejection of the upper and lowerslide blocks. The ejector blades 95 engage the molded rack at pointsspaced along the front edge of the intermediate tier. In FIG. 9, it mustbe observed again that the face of the right core slide 70, which isvisible and appears to be disposed beneath ejector blade 95, is, infact, displaced backward from the plane of the FIGURE and, hence,completely away from the molded rack. This relative position is shown inFIG. 10. To obtain this action, the sequence of the mold opening andejection is as follows. First, the mold is fully opened to the positionshown in FIG. 8. Then the left core slide 60 and right core slide 70 arewithdrawn by conventional hydraulic apparatus (not shown). Thereafter,the upper slide block 80 and lower slide block 90 are cammed off by theaction of the angular ejector pins 81 and 92 and the molded rack isejected by the action of the ejector blades 95, all of which areactuated simultaneously by the action of the ejector box 85.

Although the mold has been described in its preferred embodiment, forthe formation of the preferred embodiment of the inventive three-tieredrack for holding test tubes, it is to be understood that the inventiveconcepts embrace a mold for forming a single-piece rack having more thanthree tiers. For example, the top tier of the rack illustrated in FIG. 1could easily be formed as a second intermediate tier by first providingbottom bar-forming channels in the upper surfaces 49 and 37 of the rearand front slides. A top set of bars would then be formed over thisbottom set of bars by stacking an additional core slide (or a pair ofcore slides) over the left and right core slides 60 and 70. To form thetop bars on this second intermediate tier, this additional slide orslides would have channels milled in the lower surface or surfaces. Thetop tier above this intermediate tier could be formed, for example, by acooperative arrangement similar to the cooperative action of the upperslide block 80 and the upper surfaces 37 and 49 of the front and rearslides.

It is also to be appreciated that the number of slides may be increasedand oriented at various angles relative to one another and suitablychanneled to provide a wide variety of configurations to theintermediate tier. Such additional slides, or even the illustratedslides, may also be modified to provide other than a rectangularperiphery for one or more of the tiers. Such modifications may beparticularly desirable where the mold is to be used to provide a rackthat is to be used for purposes other than holding test tubes. Forexample, such modifications may be useful in packaging, storage, andshipping of various kinds of containers for liquids and the like. It isfully intended that the inventive concepts for both the rack and moldnot be limited merely to the holding of test tubes.

The present invention has been described in relation to its preferredembodiments. One of ordinary skill, after reading the foregoingspecification, will be able to effect various changes and substitutionsof equivalents without departing from the broad concepts disclosedherein. It is therefore intended that the protection afforded by LettersPatent granted hereon be limited only by the definition contained in theappended claims and equivalents thereof.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A single-piece injectionmolded rack comprising:a plurality of spaced-apart superposed tiersincluding a top tier, a bottom tier, and an intermediate tier, saidintermediate tier being disposed between said top and bottom tiers, saidtop tier including apertures, said intermediate tier having a top set ofbars and a bottom set of bars, selected bars within said top set beingsuperposed over and intersecting with selected bars within said bottomset to define apertures, selected apertures in said intermediate tierbeing operatively aligned with selected apertures in said top tier;first support means for interconnecting said top tier and saidintermediate tier; and second support means for interconnecting saidintermediate tier and said bottom tier.
 2. The rack of claim 1, whereineach of said tiers includes a peripheral portion defining edges, theedges of said top tier being aligned with the edges of said intermediatetier, the edges of said intermediate tier being aligned with the edgesof said bottom tier, and wherein:said first support means interconnectsa selected portion of the edges of said top tier with a selected portionof the edges of said intermediate tier; and said second support meansinterconnects a selected portion of the edges of said intermediate tierwith a selected portion of the edges of said bottom tier.
 3. The rack ofclaim 1, wherein each of said tiers includes a peripheral portion havingopposed front and rear edges and opposed left and right side edges; thefront, rear, left side, and right side edges of the top tier beingaligned with the front, rear, left side, and right side edges,respectively, of the intermediate tier; and wherein the front, rear,left side, and right side edges of the intermediate tier are alignedwith the front, rear, left side, and right side edges, respectively, ofthe bottom tier, and wherein:said first support means is located inwardfrom the respective edges of said top and intermediate tiers.
 4. Therack of claim 1, wherein each of said tiers includes a peripheralportion having opposed front and rear edges and opposed left and rightside edges; the front, rear, left side, and right side edges of the toptier being aligned with the front, rear, left side, and right sideedges, respectively, of the intermediate tier; and wherein the front,rear, left side, and right side edges of the intermediate tier arealigned with the front, rear, left side, and right side edges,respectively, of the bottom tier, and wherein:said second support meansis located inward from the respective edges of said intermediate andbottom tiers.
 5. The rack of claim 4, wherein said first support meansis located inward from the respective edges of said top and intermediatetiers.
 6. The rack of claim 1, wherein said top set of bars comprisesgroups of bars, the bars within each group being substantially parallel.7. The rack of claim 1, wherein said bottom set of bars comprises groupsof bars, the bars within each group being substantially parallel.
 8. Therack of claim 7, wherein said top set of bars comprises groups of bars,the bars within each group being substantially parallel.
 9. The rack ofclaim 1, wherein the bars within said top set are substantially parallelto one another and wherein the bars within said bottom set aresubstantially parallel to one another.
 10. The rack of claim 9, whereinsaid top and bottom bars extend between edges of said intermediate tier.11. The rack of claim 10, wherein each bar of said top set intersectseach bar of said bottom set at substantially right angles.
 12. The rackof claim 1, wherein each bar of said top set intersects each bar of saidbottom set at substantially right angles.
 13. The rack of claim 3,wherein:each of the bottom bars of said intermediate tier has asubstantially planar upper surface; and each of the top bars of saidintermediate tier has a substantially planar lower surface.
 14. The rackof claim 13, wherein the upper surfaces of said bottom bars aresubstantially coplanar with one another.
 15. The rack of claim 13,wherein the lower surfaces of said top bars are substantially coplanarwith one another.
 16. The rack of claim 13, wherein the upper surfacesof said bottom bars and the lower surfaces of said top bars aresubstantially coplanar with one another.
 17. The rack of claim 1,wherein each of said tiers includes a peripheral portion having opposedfront and rear edges and opposed left and right side edges; the front,rear, left side, and right side edges of the top tier being aligned withthe front, rear, left side, and right side edges, respectively, of theintermediate tier; and wherein the front, rear, left side, and rightside edges of the intermediate tier are aligned with the front, rear,left side; and right side edges, respectively, of the bottom tier, andwherein:the bars of said top set extend between the front and rear edgesof said intermediate tier, and the bars of said bottom set extendbetween the left side and right side edges of said intermediate tier.18. The rack of claim 1, wherein said first support means comprises:aleft side support interconnecting the left side edge of said top tierwith the left side edge of said intermediate tier; and a right sidesupport interconnecting the right side edge of said top tier with theright side edge of said intermediate tier, said second support meanscomprises: a front support interconnecting the front edge of saidintermediate tier with the front edge of said bottom tier and a rearsupport interconnecting the rear edge of said intermediate tier with therear edge of said bottom tier.
 19. The rack of claim 18, furtherincluding at least one upper spacer extending between said top tier andsaid intermediate tier, said upper spacer being positioned inwardly ofthe edges of said tiers; andfurther including at least one lower spacerextending between said intermediate tier and said bottom tier, saidlower spacer being positioned inwardly of the edges of said tiers. 20.The rack of claim 17, wherein said top tier has a substantially planarlower surface.
 21. The rack of claim 17, wherein said bottom tier has asubstantially planar upper surface.
 22. The rack of claim 21, whereinsaid top tier has a substantially planar lower surface.
 23. The rack ofclaim 17, wherein said top tier includes a lower surface having frontand rear portions, said front and rear portions each being substantiallyplanar but not coplanar with each other, said front and rear portionsintersecting at a parting line located inward from the front and rearedges of said tier and downward toward said intermediate tier.
 24. Therack of claim 23, wherein said bottom tier has a substantially planarupper surface.
 25. The rack of claim 17, wherein said bottom tierincludes an upper surface having left and right side portions, said leftand right side portions each being substantially planar but not coplanarwith each other, said left and right side portions intersecting at aparting line located inward from the left and right side edges of saidtier and upward toward said intermediate tier.
 26. The rack of claim 25,wherein said top tier has a substantially planar lower surface.
 27. Therack of claim 17, wherein:said top tier includes a lower surface havingfront and rear portions, said front and rear portions each beingsubstantially planar but not coplanar with each other, said front andrear portions intersecting at a parting line located inward from thefront and rear edges of said tier and downward toward said intermediatetier; and said bottom tier includes an upper surface having left andright side portions, said left and right side portions each beingsubstantially planar but not coplanar with each other, said left andright side portions intersecting at a parting line located inward fromthe left and right side edges of said tier and upward toward saidintermediate tier.
 28. The rack of claim 18, wherein:said left and rightside supports have substantially planar inner surfaces, said surfacesbeing disposed opposite one another and in planes which aresubstantially parallel to one another and to said top set of bars; andsaid front and rear supports have substantially planar inner surfaces,said surfaces being disposed opposite one another and in planes whichare substantially parallel to one another and to said bottom set ofbars.
 29. The rack of claim 18, wherein a portion of one of the edges ofsaid intermediate tier extends outward relative to the respective edgeof the bottom tier aligned therewith.
 30. The rack of claim 18, whereinthe front edge of said intermediate tier extends outward relative to thefront edge of said bottom tier.
 31. The rack of claim 18, wherein theedges of each tier define a generally rectangular periphery and whereineach bar of said top set intersects each bar of said bottom set atsubstantially right angles.
 32. The rack of claim 31, wherein therectangular periphery of each tier substantially corresponds in shapeand dimensions with the shape and dimensions of the rectangularperiphery of each of the other tiers.
 33. The rack of claim 32, whereinthe front, rear, left side, and right side edges of each tier arealigned substantially coplanar with the front, rear, left side, andright side edges, respectively, of each of the other tiers.
 34. The rackof claim 33, wherein said bottom tier further includes apertures,selected apertures in said bottom tier being operatively aligned withselected apertures in said top and intermediate tiers.
 35. The rack ofclaim 34, wherein said top and bottom bars define generally squareapertures.
 36. The rack of claim 35, wherein said top tier has generallysquare apertures.